Radiant gas fired burner



A. P. LOEB ETAL RADIANT GAS FIRED BURNER May 25, 1965 Filed Dec. 14, 1961 2 Sheets-Sheet` l s. N.. U M u. N TB.H O EG mom-q W WL.. A 1 PO Dh mman., H6 mm. AM

May 25, 1965 A. P. I OEB ETAI.

RADIANT GAS FIRED BURNER 2 Sheets-Sheet 2 Filed Dec. 14. 1961 R m. L maw EU mmm N .w MN Hm au MR Bo AM Y B ATTORNEYS.

United States Patent Office 3,185,204 Patented May 25, 1965 3,185,204 RADlANT GAS FREI) BURNER Abraham P. Loeb, Penn Township, Aiiegheny County, and Morgan P. OLaughlin, Pittsburgh, Pa., assignprs to Dravo Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 14, 1961, Ser. No. 159,315 2 Claims. (Cl. 158-114) The present invention relates to low pressure gas burners of the type provided with a grid over which the combustible mixture of gas and air burns uniformly to heat the grid to incandescent temperature for emitting radiant heat. The burner may be provided with conventional type shields or deflectors for directing the emitted heat horizontally or vertically upward or downward as desired, as well as at any other desired angle.

One object of the present invention is to provide a burner construction capable of producing a combustible air-gas mixture at very low gas pressures without the presence of carbon monoxide.

Another object of the invention is to provide such a burner with a grid to be heated to a temperature sufficient to emit infra-red wave lengths.

Another object of the invention is to provide a grid construction maintaining the llame upon the exposed face of the grid and preventing blow-back of the iiame onto the inner face of the grid or into the burner manifold.

A further object of the invention is to provide a novel form of manifold for such a burner.

A still further object of the invention is to provide a novel heat accumulating and reective type of screen for such burner.

These and other objects will be made apparent by the following description and drawing forming a part thereof, wherein:

FIG. 1 shows a plan View of the assembled burner;

FIG. 2 shows a vertical longitudinal section through the burner of FIG. l;

FIG. 3 shows a section through the burner of FIG. 2 taken on the lines III-HI;

FIG. 4 shows a plan View of a modified form of burner manifold;

FIG. 5 shows a section taken on lines V-V of FIG. 4;

FIG. 6 shows an end elevation of the manifold of FIG. 4;

FIGS. 7 and 8 show sections taken on lines VII- VII and VIII-VIII respectively of FIG. 5 and FIG. 9 shows a modiiied form of inner screen.

Referring 'now Iin detail to FIGS. l to 3 of the drawing, the burner is provided with a conventional injector type gas valve 1 having a suitable gas inlet 2 and a suitable gas outlet nozzle 3. The valve 1 is provided with a suitable bracket 4, such as a two or four arm spider, for mounting the nozzle 3 upon a venturi tube 5 in spaced relation to the mouth opening 6 thereof.

The tube 5 has an enlarged mouth 7 which tapers inwardly to the constriction S and then is progressively enlarged to the discharge opening 9. The tube 5 extends through one end of an open bottom manifold 1G. The manifold may be of any suitable shape, preferably rectangular, and is provided with side walls 11 and 12 which are connected by end walls 13 and 14. The tops of the side and end walls are connected by a top wall 15. The bottoms of said side and end Walls are provided with a peripheral flange 16. The tube 5 may be secured to the manifold in any suitable manner.

As best shown in FIGS. 2 and 3, the outlet opening 9 of venturi tube 5 terminates in spaced relation to manifold end wall 13. A defiector 17 suitably secured to tube 5 at one side of opening 9 is inclined in a direction across opening 9 towards manifold side wall 12. The deiiector 17 terminates short of the manifold end wall 13 and preferably does not extend entirely across the path of the combustible mixture of air and gas emitting from tube opening 9. The adjacent end wall 13 of the manifold is provided with a deflector plate 18 which overlies and rounds the corners formed by the junctures of manifold side walls 11 and 12 with the end wall 13.

The purpose of deliectors 17, 18 is to deiiect and cause the combustible air-gas mixture to reverse its flow in a direction towards the tube S so as to substantially equalize the volume and pressure of the air-gas mixture over the entire area of the manifold. The open bottom of the manifold yis closed by a plurality of spaced screens forming a grid for emitting radiant heat of infra-red wave lengths. An inner screen 19 is abutted against the manifold bottom flange 16. An outer screen 20 is connected to the same iiange 16 by suitable clamps 21 and spaced from the inner screen by spacers 22. Preferably a gasket 23 is disposed between manifold ange 16 and inner screen 19.

The combination of inner screen 19 spaced from outer screen 20 provides a plurality of advantages. Combinations of screen mesh between 20 and 60 have been tried and found to be operable. The presently preferred combination, with the burner disclosed, has been found to comprise an inner screen of 50 mesh and an outer screen of 30 mesh. The spacing between the screens, as provided by the spacers 22, is a variable determined by pressure, velocity and temperature relationships between the interior of the manifold, the screen openings and the temperature upon the outer surface of the outer screen.

The burner is designed to operate at low gas pressures and to dispense with the need for a premix blower to maintain suicient pressure in the manifold to prevent flash back of the llame. The venturi effect of low pres-- sure gas from burner 1 flowing into mouth 6 Aof tube 5 in combination with the screen mesh and wire diameters of the grid permits sufficient combustion air to beV drawn into manifold 16, through the spacing of the spider arms, to burn the fuel within safety limits of CO, without employment of secondary air.

In order for outer screen 20 to emit infra-red wave lengths of heat, the screen should be at a temperature of about 1550 F. The air-gas pressure, as previously stated, is substantially uniform within the manifold and over inner screen 19. The open area of the screen 19,

provided by the screen mesh openings, permits the airgas mixture to pass through screen 19 with a minimum resistance and can be ignited and burned upon the outer surface of outer screen 2i). The spacing between the inner and outer screens is preferably such that the two screens are maintained in spaced relation during all operating conditions. Any contact between the screens may create cold spots on the outer screen. The inner screen, in spaced relation to the outer screen, provides in effect a temperature barrier between the outer screen and the interior of the manifold preventing the air-gas mixture within the manifold reaching ignition temperature. An Vextreme spacing of the two screens may cause the flame upon the outer face of the outer screen to blow-back and burn on the outer face of the inner screen. This latter condition may result in ignition of the air-gas mixture within the manifold.

Although only an inner screen and an outer screen have been discussed as being mounted upon the manifold, the inner screen may in fact comprise two or more screens. The outer screen would in every case be disposed in spaced relation to the inner screen or screens. The plural inner screens need not be so spaced relative to each other. The said outer screen, mounted on the manifold, provides upon its outer face a burning surface for thecombustible gasair mixture moving thereto from the manifold. Any contact between the inner and outer screen would tend to cause cold spots upon the outer screen as heretofore discussed.

A modified form of inner screen 19a is shown in FIG. 9 of the drawing. Here a single screen 24 is bent twice upon itself a spaced intervals. The overlapping bent portions 25, 25a provide a triple thickness of screen and the spacing 26 between the bent portions providing a single thickness of screen. Such inner screen is provided with suitable end marginal portions for attachment to the manifold flanges with suitable spacers as shown in FIG. 2 of the drawing, This modified form of inner screen is intended to be used with an outer screen 20 of single thickness as disclosed in FIG. 2 of the drawing. Y

This modified form `of inner screen when tested upon a manifold in combination with a single at outer screen in spaced relation thereto, gave unexpected and improved results over theconstruction of FIG. 2. The combustible air-gas mixture flowing through the modified inner screen burned with a uniform flame upon the outer face of the outer screen. Additionally there appeared to be better control of the pressure drop through the screen and maintained a suitable flame under all operating conditions. Y

Referring now to FIGS. 4 tok 8 of the drawing there is shown a modified form of the manifold of FIGS. l to 3. This modied form of manifold indicated generally as 110 comprises a top wall 115,- end walls 113,114 and side walls 111, 112 preferably integrally formed as by casting. The free ends of the side `and end walls are provided with a continuous flange 116, provided withy suitable openings for attachment of the screens to be hereinafter discussed. Manifold end wall 113 is arcuate in shape and portions 116rz of the manifold flange 116 are recessed below the rectangular flange portion 116 .adjacent wall 113, as best shown in FIGS. 4 and 5.

Disposed within manifold 111 and formed integrally therewith is a venturi tube 105.I As best shown in FIG. 5,-tube 105 has an enlarged mouth opening 106 disposed outwardly of manifold wall 114 and connected with tube body 105 by tapering. mouth 107 through a suitable opening in'wall 114'and above wall 115. Tube mouth opening 106 is defined by a flange 106a having outstanding por- 'tions 106]; to which may be attached the gas valve mounting bracket 4 as shown in FIG. 1. Tube 105 has an internal opening therein of uniform diameter for a portion of its length inwardly of wall 114 and then is progressively enlarged in diameter to the tube discharge opening 109. Opening 109 extends inwardly of manifold 110 from top wall 115 thereof; As best shown in FIGS. .4, 5 and S the tube 105 integrally formed with the manifold 110, has a baille 117 at one side of tube discharge opening 109 and extending therefrom towards end wall 113 but terminating short thereof.

Baiie 117 functions to divert the air-gas mixture issuing from 109 laterally towards one manifold side wall 112 and adjacent arcuate end wall 113 to. reverse the ow of the air-gas mixture towards and over tube 105 effecting a substantially uniform pressure of the air-gas mixture throughout the manifold. As best shown in FIG. 8 baffle 117 has a concave face 117a inclined across a portion of yopening 109 and extending from manifold top wall 115 entirely across opening 109 to adjacent the plane of the flange 116. A pair of screens 19, 20 may be secured to ange 116 by means of suitable fasteners as in FIG. 2. Preferably screen 19a of FIG. 9 will be used instead of inner screen 19 of FIG. 2.

The foregoing describes a fabricated and a cast form of the preferred manifold construction. In both forms of the manifold the venturi tube 5, 105 thereof is disposed in abutting adjacent relation to the manifold top wall and in substantial spaced relation to the screens closing the bottom outlet opening of the manifold. Additionally, the venturi 5, 105 is disposed in substantial spaced relation to the manifold side walls. The deflector plates 17, 117 of both forms of the manifold extend inwardly of the manifold, from the top wall thereof, and entirely across the discharge opening 9, 109 of the venturi tube to adjacent the screens secured `to the manifold. Such defiector plate construction effects controlled deflection of substantially the entire volume of air-gas mixture emitting from the venturiY tube discharge opening without impeding the free discharge of the said mixture. In this manner a substantially uniform pressure of said mixture is maintained over the entire length of the manifold. Such construction aids uniform iiame control over the entire area of the outer manifold screen and consequently emission of heat therefrom.

A further alternate form of the inner screen 19a has been found satisfactory. Such alternate form of inner screen (not shown) is comprised of folded areas providing a multiple thickness'cf screen. Such folded areas are disposed in parallel relation without any substantial width of single thickness between the folded areas as now shown in FIG. 9 of the drawing.

Although not disclosed in the drawing, the herein de-V scribed burner is adapted for use with a known type of reverberator screen. Such a reverberator screen is customarily in the form of a flat screen suspended from the manifold iianges 16, 116 in parallel spaced relation to the herein identified outer manifold screen 20 of FIG. 2. Preferably the reverberator screen would be of Substantially the same area as screen 20, but of heavier gauge and larger mesh opening. This later screen is disposed in spaced relation to screen 20, a distance of about 1%" has proved to be satisfactory and maintains the screen Within the heat zone of the products of combustion from the llame upon the outer face of the screen 20. Such reverberator screen normally attains a temperature of about above the temperature of the screen' 20 when the burner is operating.

We claim:

r 1. An infrared gas heating burner, comprising,

a manifold portion of substantially rectangular shape having top, side and end Walls defining a gas and air mixture emitting bottom opening,

peripheral ange means yon said side and end Walls about said opening,

a venturi type gas and combustion air mixing tube disposed within said manifold,

said mixing tube being disposed adjacent said manifold top Wall with thel inlet end of the tube projecting through one end wall of the manifold and the outlet end of the tube disposed in spaced relation to the opposite end wall of the manifold,

an open mesh screen mounted upon said manifold peripheral iiange, and

a second open mesh screen overlying the rst named screen in outwardly spaced relation thereto and connected with said manifold,

means for deflecting the stream of air-gas mixture issuing from the outlet end of the mixing tube towards the juncture of the adjacent manifold end and side walls for reversing the liow of the mixture rearwardly of the manifold toV effect substantially uniform pressure of said mixture over the entire adjacent face of the manifold screen, comprising a plate like portion extending from said manifold top wall and adjacent one side of thev tube outlet opening for the height thereof and forwardly from said opening to adjacent the juncture between the adjacentl end wall and opposide side wall, and a' connection between said plate like portion and the adjacent tube.

2. An infrared gas heating burner, comprising,

`a manifold portion having a top wall and upstanding integral end and side walls dening a gas and air mixture emitting opening,

an inner open mesh screen secured to said manifold and overlying said opening thereof,

an outer open mesh screen overlying the said rst perforate screen, in outwardly spaced relation thereto, and secured to said manifold,

a venturi type gas and combustion air mixing tube disposed Withn said manifold adjacent said top Wall thereof,

one said manifold end wall having an opening therethrough receiving the inlet end of said tube and the youtlet end of the venturi tube terminating in spaced relation to the other end Wall of said manifold,

means for partially enclosing and deecting'the stream of air-gas mixture issuing from the outlet end of the mixing tube towards the juncture of the adjacent manifold side and end walls for reversing the flow of said mixture rearwardly of the manifold to eiect substantially uniform pressure of the mixture over the entire adjacent face of the manifold screen, comprisng a concave member connected with a side of the mixing tube and extending vertically from the References Cited by the Examiner UNITED STATES PATENTS 656,050 8/00 Sattler 160-14 667,614 2/01 Bradley 160-14 741,456 10/03 Cannon 158--114 2,870,830 1/59 Schwank. 3,021,893 2/62 Honger 158-116 3,040,805 6/62 Lambert. 3,084,736 4/63 Mentel et al. 158-114 V FOREIGN PATENTS 616,491 3/ 61 Canada. 826,673 1/ 60 Great Britain.

JAMES W. WESTHAVER, Primary Examiner.

FREDERICK L. MATTESON, IR., MEYER PERLEN,

Examiners. 

1. AN INFRARED GAS HEATING BURNER, COMPRISING, A MANIFOLD PORTION OF SUBSTANTIALLY RECTANGULAR SHAPE HAVING TOP SIDE, AND END WALLS DEFINING A GAS AND AIR MIXTURE EMITTING BOTTOM OPENING, PERIPHERAL FLANGE MEANS ON SAID SIDE AND END WALLS ABOUT SAID OPENING, A VENTURI TYPE GAS AND COMBUSTION AIR MIXING TUBE DISPOSED WITHIN SAID MANIFOLD, SAID MIXING TUBE BEING DISPOSED ADJACENT SAID MANIFOLD TOP WALL WITH THE INLET END OF THE TUBE PROJECTING THROUGH ONE END WALL OF THE MANIFOLD AND THE OUTLET END OF THE TUBE DISPOSED IN SPACED RELATION TO THE OPPOSITE END WALL OF THE MANIFOLD, AN OPEN MESH SCREEN MOUNTED UPON SAID MANIFOLD PERIPHERAL FLANGE, AND A SECOND OPEN MESH SCREEN OVERLYING THE FIRST NAMED SCREEN IN OUTWARDLY SPACED RELATION THERETO AND CONNECTED WITH SAID MANIFOLD, MEANS FOR DEFLECTING THE STREAM OF AIR-GAS MIXTURE ISSUING FROM THE OUTLET END OF THE MIXING TUBE TOWARDS THE JUNCTURE OF THE ADJACENT MANIFOLD END AND SIDE WALLS FOR REVERSING THE FLOW OF THE MIXTURE REARWARDLY OF THE MANIFOLD TO EFFECT SUBSTANTIALLY UNIFORM PRESSURE OF SAID MIXTURE OVER THE ENTIRE ADJACENT FACE OF THE MANIFOLD SCREEN, COMPRISING A PLATE LIKE PORTION EXTENDING FROM SAID MANIFOLD TOP WALL AND ADJACENT ONE SIDE OF THE TUBE OUTLET OPENING FOR THE HEIGHT THEREOF AND FORWARDLY FROM SAID OPENING TO ADJACENT THE JUNCTURE BETWEEN THE ADJACENT END WALL AND OPPOSIDE SIDE WALL, AND A CONNECTION BETWEEN SAID PLATE LIKE PORTION AND THE ADJACENT TUBE. 